Comfort noise (or comfort tone) is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.
In a full-duplex voice communication system, when only the far-end talker is talking, the acoustic echo cancellation and noise reduction algorithms sometimes suppress the echo and noise so well that the far-end talker hears absolute silence. When the near-end talker starts talking, some background noise may be transmitted thus providing the far-end listener with a very unnatural conversational experience. To address this problem, comfort noise is generated and transmitted to the far-end when only the far-end is talking.
Further, when transitioning between the states when comfort noise is not being played, it is desired to provide a seamless experience in terms of matching the amplitude and spectral content of the background noise as closely as possible.
U.S. Pat. No. 7,243,065 granted on Jul. 10, 2007 to Stephens et al., the entire contents of which is incorporated herein by reference, is addressed to a comfort noise generator. Unfortunately, the described comfort noise generator does not provide a high enough quality comfort noise.